Commonly owned, concurrently filed application entitled xe2x80x9cA Remotely Controllable Circuit Breaker With Combined Visual Indication of State and Manual Overridexe2x80x9d and identified by Ser. No. 09/514,103.
1. Field of the Invention
This invention relates to circuit breakers for protecting electric power circuits. More particularly, it relates to circuit breakers with a set of secondary contacts which can be remotely controlled by a latchable operator such as a magnetically latchable solenoid.
2. Background Information
Circuit breakers used in residential and light commercial applications are commonly referred to as miniature circuit breakers because of their limited size. Such circuit breakers typically have a pair of separable contacts opened and closed by a spring biased operating mechanism. A thermal-magnetic trip device actuates the operating mechanism to open the separable contacts in response to persistent overcurrent conditions and to short circuits. Usually, circuit breakers of this type for multiple circuits within the residence or commercial structure are mounted together within a load center which may be located in a basement or other remote location. In some applications, it has been found convenient to use the circuit breakers for other purposes than just protection, for instance, for load shedding. It is desirable to be able to perform this function remotely, and even automatically, such as with a computer. However, the spring powered operating mechanisms are designed for manual reclosure and are not easily adapted for reclosing remotely. In any event, the mechanisms are not designed for repeated operation over an extended period of time.
U.S. Pat. Nos. 5,301,083 and 5,373,411 describe a remotely operated circuit breaker which introduces a second pair of contacts in series with the main separable contacts. The main contacts still interrupt the overcurrent, while the secondary contacts perform the discretionary switching operations. The secondary contacts are controlled by a solenoid which is spring biased to close the contacts. The solenoid has two coils, an opening coil and a hold coil. Initially, both coils are energized to open the contacts. Power to the opening coil is then turned off, and only the holding coil remains energized. Thus, continuous power is required to keep the main contacts open. When power to the holding relay is terminated, the spring recloses the secondary contacts.
There is a need, therefore, for an improved remotely operated circuit breaker.
More particularly, there is a need for such a remotely controllable circuit breaker which does not require continuous power to maintain the contacts in either an open or closed state.
There is a further need for such a remotely controllable circuit breaker which is simple and economical.
There is still another need for such a remotely controllable circuit breaker which provides an indication of the status of the remotely controllable set of contacts.
These needs and others are satisfied by the invention which is directed to a remotely controllable circuit breaker which includes a latching solenoid to open and close the remotely controllable secondary contacts. The solenoid has a first coil which when energized operates the solenoid""s plunger to a first position which closes the set of secondary contacts and a second coil which when energized operates the plunger to a second position in which the set of secondary contacts is opened. A control circuit includes a voltage source and a first switch which selectively connects the voltage source to the first or second coil. This first switch has a common terminal to which the voltage source is connected. A first switched terminal and a second switched terminal on this first switch are alternatively selectively connected to the common terminal. The first coil of the solenoid is connected between the first switched terminal and ground through a second, remotely controlled switch. Similarly, the second coil is connected between the second switched terminal and ground also preferably through a third switch. The first switch is coupled to the plunger of the solenoid and has first contacts connected between the common terminal and the first switched terminal and second contacts connected between the second switched terminal and the common terminal. One of these contacts is normally open and the other is normally closed. These contacts in the first switch enable one of the coils of the solenoid or the other by connecting it to the voltage source. Actuation of the coil is then initiated by closure of the remotely located second or third switch. The status line is connected to one of the switched terminals so that it is energized by the single voltage source when the associated coil is enabled.
A principal object of the invention is to provide a remotely controllable circuit breaker in which the set of secondary contacts is opened and closed by momentary remotely generated signals so that continuous power is not needed to maintain the contacts in one state or the other.
It is also an object of the invention to provide such a remotely controllable circuit breaker in which the control circuitry is simple and economical to implement.